feat: Setup app lifecycle, job service and basic csv parser

app/utils/csv_parser.py

@@ -0,0 +1,70 @@
+import csv
+import io
+from datetime import datetime
+from typing import Any, Dict, List
+from app.core.exceptions import InvalidCSVException
+
+REQUIRED_COLUMNS = {"transaction_id", "date", "amount", "category", "description"}
+
+
+def parse_and_validate_csv(content: bytes) -> List[Dict[str, Any]]:
+    csv_file = io.StringIO(decoded)
+    reader = csv.DictReader(csv_file)
+
+    # Map headers to predefined required cols
+    headers = {h.strip().lower() for h in reader.fieldnames if h}
+    header_mapping = {}
+    for actual_header in reader.fieldnames:
+        cleaned = actual_header.strip().lower()
+        if cleaned in REQUIRED_COLUMNS:
+            header_mapping[cleaned] = actual_header
+        elif cleaned == "id" and "transaction_id" not in header_mapping:
+            header_mapping["transaction_id"] = actual_header
+
+    missing = REQUIRED_COLUMNS - set(header_mapping.keys())
+    if missing:
+        raise InvalidCSVException(f"Missing required CSV columns: {', '.join(missing)}")
+
+    parsed_rows = []
+    for line_num, row in enumerate(reader, start=2):
+        t_id = row.get(header_mapping["transaction_id"])
+        date_str = row.get(header_mapping["date"])
+        amount_str = row.get(header_mapping["amount"])
+        category = row.get(header_mapping["category"])
+        description = row.get(header_mapping["description"])
+
+        if not all([t_id, date_str, amount_str, category, description]):
+            raise InvalidCSVException(f"Row {line_num}: Empty values are not allowed in required fields")
+
+        try:
+            amount = float(amount_str.strip())
+        except ValueError as e:
+            raise InvalidCSVException(f"Row {line_num}: Invalid amount '{amount_str}'. Must be a number.") from e
+
+        parsed_date = None
+        for fmt in ("%Y-%m-%d", "%m/%d/%Y", "%d-%m-%Y", "%Y/%m/%d"):
+            try:
+                parsed_date = datetime.strptime(date_str.strip(), fmt).date()
+                break
+            except ValueError:
+                continue
+
+        if not parsed_date:
+            raise InvalidCSVException(
+                f"Row {line_num}: Invalid date format '{date_str}'. Expected YYYY-MM-DD or MM/DD/YYYY"
+            )
+
+        parsed_rows.append(
+            {
+                "transaction_id": t_id.strip(),
+                "date": parsed_date.isoformat(),
+                "amount": amount,
+                "category": category.strip(),
+                "description": description.strip(),
+            }
+        )
+
+    if not parsed_rows:
+        raise InvalidCSVException("CSV file contains no data rows")
+
+    return parsed_rows